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PDF page size: A4 vs Letter vs A3 and how to choose

Published 2026-09-09 · Education

You open a PDF and it looks fine on screen, then you print it and half the page is cut off or the margins are huge. Often the cause is a mismatch of page size: the file was made for A4 and your printer expects Letter, or vice versa. This guide explains the common sizes, when each one is used and how to get a document that prints the way you expect.

The sizes you will actually meet

Three sizes cover almost every document you handle. A4 is the standard paper in most of the world, measuring 210 x 297 mm, and it is the default for European, Asian and Australian documents. Letter is the North American size at 8.5 x 11 inches, which is slightly shorter and wider than A4. A3 is exactly twice A4, so 297 x 420 mm, and it is used for posters, plans and anything that needs a large canvas. Every other page size is a variation on these.

Why a document prints the wrong size

A PDF carries its page size inside the file, and printers use that value to decide how to fit the pages. When a file was built for A4 and your printer is set to Letter, the printer may scale it, cut the edges or add white borders, which is exactly the cut-off and margin problem you see. The mismatch is not a damaged file, it is a size handshake gone wrong between the file and the printer.

Pick the size by where the document goes

Match the page size to the audience. For client work mostly going to Europe, Asia or Australia, use A4. If your audience is North American, use Letter so it prints full-bleed on their printers. For posters, large plans and printed banners, A3 gives you the room. When in doubt, stay with A4, which is the international default and the least likely to surprise a recipient with a form or a chunky print area.

Fix a file that came out the wrong size

If a document arrived in the wrong size, you usually do not need to rebuild it. The fastest fixes involve only the orientation and the print setup: a file that prints sideways can be corrected with rotate a PDF, and one that is too wide can be scaled to fit in the print settings rather than re-created. When a paper copy is what you need, exporting through the print to PDF route with Fit to Page set gives you a version sized for your printer.

Rebuild a document at the size you want

When the source is images, you control the page size directly. Gather your pages with Images to PDF and choose the output size, so a scan or a photo becomes an A4 or A3 document at the size you specify instead of inheriting a random default. Combine that with printing at the right scale and you get exactly the sheet you planned. For very large scans, compress the PDF afterwards keeps the file manageable.

Resolution and size work together

Page size and resolution are two parts of the same question. A large A3 page holding a low-resolution image will look pixelated when printed, as covered in the guide to PDF, print and DPI resolution. The rule of thumb: choose a large enough page to hold your content comfortably, then make sure the images carry enough resolution to stay sharp at that size. Get both right and the file prints exactly as you designed it.